<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        setTimeout(()=>{
            console.log(1);
        },0)
        new Promise((resolve,reject)=>{
            console.log(2);
            resolve()
        }).then(()=>{
            console.log(3);           
        }).then(()=>{
            console.log(4);           
        })
        console.log(5);
        // 2 5 3 4 1
    </script>
</body>
</html>